Lampard warned Abraham to keep up his good form or risk losing his place to Olivier Giroud and Michy Batshuayi in the team.
Tammy Abraham gave the Premier League side the lead, but Lille levelled before half-time through Victor Osimhen.
Willian settled the affair with a 77th-minute volley at the Stade Pierre Mauroy.
“Tammy’s performance was more of the same. He’s hungry for goals, he’s physical, he gives everything for the team and he has quality when the ball is at his feet,” Lampard told Chelsea’s website.
“Of course, there’s improvement to be had but he’s showing that. The minute Tammy’s levels drop, then we look next to Giroud and Batshuayi, and can they come in and make a difference.
“We will see many more Champions League goals from him I hope, and many more performances like tonight.”
